DynamicJasper Groups with Grand Total

[vbini21]

I want to have the grand total below the group totals. Been trying it out for long and its still not working. My code is as below

GroupBuilder gb1 = new GroupBuilder();
DJGroup g1 = gb1.setCriteriaColumn((PropertyColumn) columnCategory)
.setGroupLayout(GroupLayout.VALUE_IN_HEADER)
.addFooterVariable(columnAmount, DJCalculation.SUM)
.setFooterVariablesHeight(new Integer(20))
.setFooterHeight(new Integer(50), true)
.setHeaderVariablesHeight(new Integer(35))
.setDefaultHeaderVariableStyle(titleStyle)
.build();
GroupBuilder gb2 = new GroupBuilder();
DJGroup g2 = gb2.setCriteriaColumn((PropertyColumn) columnSummation)
.addFooterVariable(columnAmount, DJCalculation.SUM)
.build();

report1.getReportBuilder().addGroup(g1);
report1.getReportBuilder().addGroup(g2);

Any assistance?